Song Key Finder
Drop in a track and find out what key it is in. No signup, no upload, no limit.
Got the key? Melodious turns the whole track into a music video — See how
Drop an audio file to find its key
MP3, WAV, M4A, FLAC or OGG
Your file never leaves your browser — the analysis runs on your device and nothing is uploaded.
How to find the key of a song
To find what key a song is in, drop the audio file onto the tool above. It measures which of the twelve notes the music actually uses, weighs that against the note patterns that define each major and minor key, and returns the best fit — usually in a few seconds. Nothing is uploaded; the file is read and analysed on your own device, so it works offline and needs no account. The result comes with a confidence rating, and when the runner-up is the relative major or minor — the key built from exactly the same seven notes — the tool says so instead of picking one and sounding certain. That pair is the single most common mistake any key detector makes, human or automatic.
How the detection actually works
A key is defined by which notes a piece of music uses and which of them it treats as home. So the first step is counting notes. The tool takes the audio apart into its frequencies many times across the track, folds every frequency onto one of the twelve note names — every A, in every octave, counts towards A — and adds up how much energy each one carries. The result is a twelve-bar histogram of the song's note content, and it is shown alongside every answer.
The second step is matching. Each of the twenty-four keys has a characteristic profile: in a major key the tonic, the fifth and the third dominate, in that order, and the notes outside the scale barely appear. Those profiles come from listening experiments conducted by Carol Krumhansl and Edward Kessler in 1982, in which musicians rated how well each note fitted an established key. Comparing the song's histogram against all twenty-four and taking the closest match gives the key.
That is also where the method's limits come from, and they are worth knowing before you trust a result.
Why key detection gets relative major and minor confused
C major and A minor contain identical notes. So do G major and E minor, and every other relative pair. If a key were only its note content, these would be the same key — and a method built on counting notes cannot fully tell them apart, because there is nothing in the count to tell apart.
What separates them is emphasis: which note the music keeps returning to, which chord it ends on, what feels like rest. Those show up faintly in the histogram — a song in A minor really does spend more time on A — and that faint signal is what the profiles measure. It works often enough to be useful and not often enough to be certain, which is why this tool tells you when the two were close rather than picking one and sounding sure.
When it flags a close call, use your ear. Play the song and hum the note it comes to rest on at the end of a phrase. That note is the tonic, and it settles the question in about ten seconds — faster and more reliably than any amount of extra computation.
Two other cases are worth knowing. Songs that change key get a single answer for the whole file, which will be whichever key dominates. And heavily percussive or distorted material can obscure the notes entirely, in which case the tool reports low confidence or no key at all rather than inventing one.
Frequently asked questions
How do I find out what key a song is in?
Drop the audio file onto the tool on this page. It analyses the notes present across the whole track and matches them against the twenty-four possible major and minor keys, returning the best fit with a confidence rating. If you would rather do it by ear, play the song and hum the note it feels like it comes to rest on — that note is almost always the tonic, and whether the song sounds bright or sad tells you major or minor.
Is it free, and do I need an account?
It is free with no account and no limit. The analysis is code running in your browser rather than a service we pay for per use, which is why it can stay open rather than metered.
Does my music get uploaded?
No. Your browser reads the file and analyses it on your device; nothing is sent to a server. You can verify this by watching your browser's network tab while you use it, or by disconnecting from the internet after the page loads — it still works.
Why did it say C major when I think the song is A minor?
Because those two keys contain exactly the same seven notes. C major and A minor are what musicians call a relative pair, and no amount of counting notes can fully separate them — the difference is which note the music treats as home, which is a matter of emphasis and resolution rather than note content. The tool weighs that emphasis and will tell you when the call was close. When it flags a close call, trust your ear: play the song and notice which of the two notes it settles on.
How accurate is it?
On a track that stays in one key with clear harmonic content, it is dependable. Accuracy drops on songs that change key partway through (only one key is reported for the whole file), on heavily distorted or percussive material where the notes are obscured, and on music that leans on one chord for long stretches. Rather than hide that, every result is labelled high, medium or estimated confidence, and the note histogram it derived the answer from is shown so you can sanity-check it yourself.
What audio formats work?
MP3, WAV, M4A, FLAC and OGG generally work. Decoding is handled by your browser, so support varies slightly between Chrome, Safari and Firefox. If a file is refused, converting it to WAV or MP3 fixes it.
What do I need a song's key for?
Writing a part that fits, picking a sample or acapella that will sit in tune with a track, transposing a song into a range you can actually sing, harmonically mixing one record into the next as a DJ, and choosing the right backing track or chord chart for a cover.
You have the key. Want the video?
Attach a track and describe what you want in one message. An AI director storyboards it scene by scene, with the same character in every shot. Your first project's keyframes are free, so you see the whole storyboard before deciding to render.
Start your videoLooking for something else? Find a song's BPM · AI music video generator · AI lyric video maker